CN116865849B - High-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method and device - Google Patents
High-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method and device Download PDFInfo
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Abstract
The invention relates to a high torsion rate weak coupling multi-core optical fiber crosstalk detection method, which comprises the steps of constructing a torsion correction coefficient based on the torsion rate of an optical fiber and the core distance between an incident optical fiber and an interfered optical fiber, and acquiring a correction propagation constant based on an equivalent propagation constant; based on a coupling mode theory, introducing the influence of the bending radius of the optical fiber, the torsion rate of the optical fiber and random structural fluctuation, and constructing an updated coupling mode equation; dividing the weakly coupled multi-core optical fiber into N equal-length uncorrelated uniform sections, calculating the electric field slow-change amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber to obtain an inter-core crosstalk power expression, and then obtaining the inter-core crosstalk expression after correcting the propagation constant difference; substituting the corresponding power spectrum density function into an inter-core crosstalk expression to obtain an inter-core crosstalk calculation model; substituting N, the mode coupling coefficient, the longitudinal propagation distance, the length of each optical fiber section, the preset relevant length and the correction propagation constant difference into the inter-core crosstalk calculation model to obtain a crosstalk value.
Description
Technical Field
The invention relates to the technical field of optical fibers, in particular to a high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method, a device and a computer-readable storage medium.
Background
In the twenty-first century, with the popularization of the mobile network and the development of the internet hot trend, the social production life and the intelligence are deeply bound, and thus the data flow in ten years is increased by about 100 times. In recent years, due to the arrival of the 5G age, the universal broadband service system is energized for business fields such as everything interconnection, virtual reality, unmanned operation and the like, and the global average broadband service rate is expected to be increased from 46Mbps in 2018 to 110Mbps in 2023, which necessarily puts higher demands on the communication system. With the application of time division multiplexing, wavelength division multiplexing, polarization multiplexing and other technologies, modern communication transmission rates based on single-mode single-core optical fibers (SM-SCF) rapidly approach to a limit value of 100Tb/s of nonlinear shannon from tens of Mb/s in the past. Therefore, how to break through the traffic demand bottleneck of the communication system of the next stage, the capacity shrinkage problem is expected to occur in the near future, and thus new demands are made on the communication capacity of the optical fiber.
The main way to increase the transmission capacity in the optical fiber is to increase the transmission capacity of a single channel and increase the number of channels, and the signals can be modulated and multiplexed from five physical dimensions of time, frequency, polarization, complex amplitude and space, but the previous technologies have been deeply explored, and break through of greatly increasing the signal capacity has been very difficult. Therefore, the last dimensional spatial multiplexing has been proposed and attracted a lot of researchers, and as a solution to the capacity saturation problem of the conventional SM-SCF, the most direct method of a transmission system based on Space Division Multiplexing (SDM) is to increase the number of cores or modes in one optical fiber. Currently, there are three dominant implementations of increasing SDM spatial paths, multi-core fiber (MCF), multi-mode fiber (MMF), few-mode multi-core fiber (FM-MCF). MCF has good application prospect, but put many fiber cores in limited cladding space, lead to each fiber core between the distance can be very little for the optical signal that transmits at fiber core can influence other adjacent fiber cores, influences the quality of optic fibre communication, namely the crosstalk phenomenon between the fiber cores. Therefore, it is a significant problem to study how to suppress crosstalk between neighboring cores during MCF.
The majority of current research on crosstalk is based on the theory of coupling mode and the theory of coupling power, and MCF crosstalk estimation in most research needs to provide deterministic values of parameters affecting crosstalk, such as bend radius and twist rate, and most are not applicable to estimation of high twist rate fibers. However, the bending radius and the torsion rate of the actually laid optical fiber are not constant, and there may be some influence of random structural fluctuations such as temperature, environment, etc., which may cause a large error in crosstalk estimation if the previous method is used. Therefore, we need to add the effects of torsional velocity and random structural fluctuations to the original coupling mode equation, so as to derive a coupling power equation suitable for crosstalk under practical conditions, and use the coupling power equation to analyze the effect of crosstalk on the multi-core fiber.
In summary, the conventional crosstalk estimation needs to input a fixed bending radius and torsion rate, but the bending radius and torsion rate of the actually laid optical fiber are affected by random structural fluctuations and are not a fixed value, so that the error of the calculation result of the crosstalk under the actual situation is larger.
Disclosure of Invention
Therefore, the invention aims to solve the technical problem that the calculated crosstalk error is large because the influence of random structural fluctuation on the bending radius and the torsion rate of the optical fiber is not considered in the prior art.
In order to solve the technical problems, the invention provides a high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method, which comprises the following steps:
based on the fiber torsion rate and the fiber core distance between the incident fiber and the interfered fiber, constructing a torsion correction coefficient for representing the influence of the torsion rate on the refractive index;
Acquiring a correction propagation constant based on the equivalent propagation constant according to the torsion correction coefficient;
Based on a coupling mode theory, introducing a correction propagation constant difference representing the bending radius of the optical fiber and the torsion rate of the optical fiber and a phase function representing the influence of random structural fluctuation to construct an updated coupling mode equation between an incident optical fiber and an interfered optical fiber of the weakly-coupled multi-core optical fiber;
dividing the weakly coupled multi-core optical fiber into N irrelevant uniform sections with equal length, and calculating electric field slow-change amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber based on the updated coupling mode equation;
Acquiring an inter-core crosstalk power expression of the optical fiber section according to the electric field slow-change amplitude change in the same optical fiber section of the incident optical fiber and the interfered optical fiber;
Based on the correction propagation constant difference between the incident optical fiber and the interfered optical fiber and the inter-core crosstalk power expression, obtaining the inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber;
Substituting a power spectrum density function corresponding to a random process of random structural fluctuation into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model;
Substituting the total number N of segmented segments of the weakly coupled multi-core optical fiber, the mode coupling coefficient, the longitudinal propagation distance, the length of each optical fiber segment, the preset correlation length and the correction propagation constant difference into an inter-core crosstalk calculation model to obtain a high-torsion-rate weakly coupled multi-core optical fiber crosstalk value.
In one embodiment of the present invention, the torsion correction coefficient characterizing the influence of the torsion rate on the refractive index is constructed based on the fiber torsion rate and the core distance between the incident fiber and the interfered fiber, and is expressed as:
Where D represents the core distance of the incident fiber from the interfered fiber and γ represents the fiber twist rate.
In one embodiment of the present invention, the obtaining the correction propagation constant based on the equivalent propagation constant according to the torsion correction coefficient includes:
angle of bend radial
Substituting the bending radial angle and the torsion correction coefficient k t into an expression of an equivalent propagation constant to obtain a correction propagation constant expression, wherein the correction propagation constant expression is expressed as:
Wherein, An initial phase established on a Cartesian coordinate system on a cross section of a weakly coupled multi-core optical fiber, wherein R represents the bending radius of the optical fiber; the equivalent propagation constant differences Deltabeta eq,mn＝βeq,m-βeq,n,βeq,m and beta eq,n respectively represent the equivalent propagation constants of the incident optical fiber m and the interfered optical fiber n, and the expression is thatThe undisturbed core propagation constant β c＝neff2π/λ,neff is the effective refractive index of the fundamental mode, λ is the wavelength of light, and (r, θ) is the angle of the local polar coordinates on the cross section of the weakly coupled multicore fiber in the bending radial direction.
In one embodiment of the invention, the updated coupling equation is expressed as:
Wherein, A m (z) and A n (z) respectively represent the electric field slow-changing amplitude of the incident optical fiber and the interfered optical fiber; z represents a longitudinal propagation distance, z=i×d, n=l/d, L is a fiber length of the weakly coupled multi-core fiber, N represents a total number of segments into which the weakly coupled multi-core fiber is divided, and d represents a length of each fiber segment; j represents a complex number, and K mn (z) represents a mode coupling coefficient from the incident optical fiber m to the interfered optical fiber n; Δβ eq,nm' represents the corrected propagation constant difference between the incident fiber m and the disturbed fiber n core, and is used to characterize the effect of fiber bend radius and fiber twist rate, expressed as:
let the incident optical fiber m be the central core and the interfered optical fiber n be the surrounding cores, correct the propagation constant difference to rewrite as:
f mn (z) denotes a phase function for describing the influence of random structural fluctuations, which is a smooth random process along the propagation direction.
In one embodiment of the present invention, the dividing the weakly coupled multicore fiber into N equal length uncorrelated uniform segments, calculating the electric field slowly varying amplitude variation in the same fiber segment of the incident fiber and the interfered fiber based on the updated coupling mode equation, includes:
Dividing the weakly coupled multi-core optical fiber into N uncorrelated uniform segments with equal length, ignoring the optical fiber transmission loss, and representing the amplitude A m (z) of the incident optical fiber m as A m(z)＝Am (0) =1; the amplitude a n (z) of the disturbed fiber n is denoted as a n (0) =0, and a n (z) < 1;
In the optical fiber segment [ z 1,z2 ], the power increase of the interfered optical fiber n is equivalent to the power increase of the inter-core crosstalk in the optical fiber segment [ z 1,z2 ], and is obtained according to the updated coupling mode equation, under the condition of low crosstalk, the electric field slowly-changing amplitude in the optical fiber segment [ z 1,z2 ] is changed into:
wherein β eq,m 'and β eq,n' represent corrected propagation constants of the incident optical fiber m and the interfered optical fiber n, respectively.
In one embodiment of the present invention, the obtaining the inter-core crosstalk power expression of the optical fiber section according to the electric field slowly changing amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber is expressed as follows:
Wherein, the expression is used for taking the average, Is an autocorrelation function of f nm (z), Δz=z 2-z1; z' represents an integral variable consistent with the z integral range; Δβ eq,nm' represents the corrected propagation constant difference between the incident optical fiber m and the interfered optical fiber n core.
In one embodiment of the present invention, the obtaining the inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber based on the corrected propagation constant difference between the incident optical fiber and the interfered optical fiber and the inter-core crosstalk power expression is expressed as:
Wherein i=1, 2,3,., N, β eq,n,i 'and β eq,m,i' are the equivalent propagation constants of the i-th section of interfered optical fiber N and the incident optical fiber m, respectively; z represents a longitudinal propagation distance, z=i×d, n=l/d, L is a fiber length of the weak-coupling multi-core fiber, and N represents a total number of segments of the weak-coupling multi-core fiber that are segmented; k nm,i (z) represents the mode coupling coefficient of the interfered optical fiber n and the incident optical fiber m in the i-th segment.
In one embodiment of the present invention, substituting the power spectral density function corresponding to the random process of random structural fluctuation into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model includes:
The power spectral density function of a random process that utilizes fourier transforms to obtain random structural fluctuations is expressed as:
Substituting the calculated model into the inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber to obtain an inter-core crosstalk calculation model, wherein the calculated model is expressed as follows:
the preset correlation length l c represents a parameter of a power spectrum density function of a random process representing random structural fluctuation after Fourier transformation, and the numerical value of the parameter represents the influence of the random structural fluctuation.
The embodiment of the invention provides a high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection device, which comprises:
The correction propagation constant acquisition module is used for constructing a torsion correction coefficient representing the influence of the torsion rate on the refractive index based on the fiber torsion rate and the fiber core distance between the incident fiber and the interfered fiber; acquiring a correction propagation constant based on the equivalent propagation constant according to the torsion correction coefficient;
The updated coupling mode equation construction module is used for introducing correction propagation constant differences representing the bending radius and the torsion rate of the optical fiber and representing phase functions influenced by random structural fluctuation based on a coupling mode theory to construct an updated coupling mode equation between an incident optical fiber and an interfered optical fiber of the weakly coupled multi-core optical fiber;
The inter-core crosstalk power calculation module is used for dividing the weakly coupled multi-core optical fiber into N irrelevant uniform sections with equal length, and calculating the electric field slow-change amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber based on the updated coupling mode equation; acquiring an inter-core crosstalk power expression of the optical fiber section according to the electric field slow-change amplitude change in the same optical fiber section of the incident optical fiber and the interfered optical fiber;
The inter-core crosstalk calculation model acquisition module is used for acquiring an inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber based on the correction propagation constant difference between the incident optical fiber and the interfered optical fiber and the inter-core crosstalk power expression; substituting a power spectrum density function corresponding to a random process of random structural fluctuation into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model;
the inter-core crosstalk value calculation module is used for substituting the inter-core crosstalk calculation model according to the total number N of segmented segments of the weakly coupled multi-core optical fiber, the mode coupling coefficient, the longitudinal propagation distance, the length of each optical fiber segment, the correlation length and the correction propagation constant difference to obtain the high-torsion-rate weakly coupled multi-core optical fiber crosstalk value.
The embodiment of the invention provides a computer readable storage medium, wherein a computer program is stored on the computer readable storage medium, and the computer program realizes the steps of the high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method when being executed by a processor.
Compared with the prior art, the technical scheme of the invention has the following advantages:
According to the high-speed weak-coupling multi-core optical fiber crosstalk detection method, the influence of the bending radius of the optical fiber, the torsion speed of the optical fiber and random structural fluctuation is introduced to construct an updated coupling mode equation, the influence of the uncertain random structural fluctuation is represented by a phase function, the influence of the bending and torsion of the optical fiber is represented by a propagation constant difference, the error estimation of the influence of the traditional model on the torsion speed is made up, the influence of the random structural fluctuation caused by bending, torsion and environment in the actual laying process of the optical fiber is considered, and the calculation accuracy of crosstalk values is improved. Based on the coupling mode equation of the influence to be considered in the linear region, a coupling power equation is constructed to calculate multi-core optical fiber crosstalk, the multi-core optical fiber crosstalk calculation is more suitable for the practical optical fiber laying condition, the application range is wider, and the multi-core optical fiber crosstalk calculation method is suitable for not only the phase matching region but also the non-phase matching region, and is also suitable for homogeneous and heterogeneous multi-core optical fibers.
Drawings
In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings, in which
FIG. 1 is a flow chart of the steps of the method for detecting crosstalk of a high-torsional-rate weakly-coupled multi-core optical fiber provided by the invention;
FIG. 2 is a schematic diagram of a dual core fiber mode coupling provided by the present invention;
FIG. 3 is a schematic view of the bending and twisting of a seven-core optical fiber provided by the present invention;
FIG. 4 is a graph showing the comparison of crosstalk with the bend radius of an optical fiber at a twist rate γ=1π/m provided by the present invention;
FIG. 5 is a graph showing the comparison of crosstalk with the bend radius of an optical fiber at a twist rate γ=50pi/m provided by the present invention;
FIG. 6 is a graph comparing simulation results of crosstalk as a function of fiber twist rate in a phase matching region provided by the present invention;
FIG. 7 is a graph comparing simulation results of crosstalk as a function of fiber twist rate in a non-phase matching region provided by the present invention;
FIG. 8 is a schematic diagram showing the comparison of the crosstalk variation between SAM calculation results and numerical simulation results at different torsion rates according to the present invention;
Fig. 9 is a graph showing the crosstalk versus the bending radius of the optical fiber at different preset correlation lengths l c at a torsional rate γ=0.01 pi/m provided by the present invention;
Fig. 10 is a graph showing the crosstalk versus the bending radius of the optical fiber at different preset correlation lengths l c at a torsional rate γ=100deg.pi/m provided by the present invention;
FIG. 11 is a graph showing the propagation constant difference with or without torsional influence provided by the present invention;
FIG. 12 is a graph of relative error as a function of segment length as provided by the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
The majority of crosstalk research today is based on the theory of coupled modes and the theory of coupled power:
1. Theory of coupled mode
The coupling equation is expressed as:
Wherein A is the complex amplitude of the slowly varying electric field, N is the fiber core number, and K mn (z) is the core N-to-core m coupling coefficient; f mn (z) is a random structural fluctuation function between core m and core n, and β m and β n are propagation constants of core m and core n, Δβ eq,mn＝βeq,m-βeq,n, respectively.
Analysis is carried out through a coupling die equation, so that a crosstalk expression is obtained, and the cross-talk expression is widely applied and mainly comprises a discrete change model (1) and a numerical model (2):
(1) Based on the random characteristics of longitudinal disturbance, 2011, tetsuya Hayashi et al manually solve the problem of random evolution of crosstalk, analyze the statistical characteristics of coupling crosstalk in a dual-core optical fiber with constant bending rate by adopting a probability statistical method, and obtain a general expression of the coupling crosstalk. It is assumed that the initial electric field amplitudes of the incident and coupled cores m and n are 1.0 and 0.0, respectively; under the condition of weak coupling, the coupling crosstalk amount is lower at this time, and the coupling crosstalk value is approximately obtained by the following discrete transformation model under the assumption that the amplitude of the incident fiber core m is always unchanged;
Amplitude a of the N post-coupling cores N at N phase matching points:
Wherein, n=lγ/pi, L is the fiber length; phi rnd represents the random phase matching between the incident and coupled cores m, n and is always assumed to be uniformly distributed between 0,2 pi. Here, since the crosstalk value is assumed to be very low (|a n,N | < 1), a m,N may be approximately a m,0 =1; where k is the coupling coefficient, β is the propagation constant, D nm represents the distance between the incident core m and the coupled core n, and R and γ represent the bend radius and twist rate, respectively; from the theory of central limits, the real and imaginary parts of the electric field amplitude of the coupled core N follow a Gaussian distribution, and when N is sufficiently large, its variance is
Thus, the mathematical expression for the resulting average crosstalk XT u is:
as can be seen from the above equation, the average power of the inter-core crosstalk varies linearly with the bend radius and the transmission length in the phase matching region.
(2) In 2018 Lin Gan et al propose a numerical solution for solving the coupling equation directly by using a computer, in which a fourth-order Dragon-Gregory-tower method and a Simpson integration method are combined to process the problem of phase integration in the coupling equation, so as to realize the numerical solution of the coupling equation.
In summary, in most practical problems, power exchange between modes is often concerned, and describing the problem according to the coupling mode equation based on crosstalk calculation of the coupling mode theory generates more unnecessary information, such as phase information, so that the problem is very complex; and neither take into account the effects of bending and torsion during the actual transmission.
2. In the coupled mode theory, the optical power in each fiber is continuously coupled to each other in a fluctuation manner along the z direction. However, when the actual length of the fiber exceeds several tens of meters, the fiber coupling no longer exhibits such fluctuations due to irregularities caused by bending and stress fluctuations during actual laying and use. In this case, the coupled power theory is more efficient and accurate; the main accepted methods are average power coupling coefficient method (1) and average crosstalk power method (2):
(1) Average power coupling coefficient method:
considering the irregularities of bending and stress fluctuation of the optical fiber in the actual use process, the coupling mode equation can be written as:
Where f (z) is a phase function describing the actual bending (bending radius R b) and torsion effect (torsion rate γ);
The coupled power equation is obtained through a series of deductions:
Let the average power coupling coefficient between the incident core m and the coupled core n be:
the coupled power equation is rewritten as:
Solving for crosstalk between an incident fiber m and a coupled fiber n at a distance L is expressed as:
XT＝tanh(hmnL)。
(2) Average crosstalk power method:
In the derivation of the coupled power theory, the integral can be solved using a Bessel function, which expands as follows:
And solving the amplitude A n,N of the coupling optical fibers N after N phase matching by utilizing a Bessel expansion method, and obtaining an electric field slowly-varying amplitude function:
and (3) taking the modulus square of the electric field slowly-varying amplitude function to obtain an average crosstalk power expression:
wherein, represents taking average, power spectral density function Expressed as:
in summary, crosstalk calculation based on the theory of coupling power, while considering bending and stress fluctuation changes, and temperature and environmental changes brought about in the actual fiber laying process; but does not take into account the effects of fiber bending, torsion and structural fluctuations on the fiber propagation constant. Propagation constants in the coupled power theory do not add bending, torsion, and random structural fluctuations influencing factors. And it needs to provide a deterministic influencing parameter, but the actual laid fiber influencing parameter is not a fixed value, so the above model cannot correctly describe the effect of torsion, which makes it unsuitable for high-torsion-rate fibers, and does not conform to the actual fiber transmission situation. Therefore, the invention re-derives the coupling power equation incorporating bending, torsion and random structural fluctuations effects and derives a new crosstalk estimation model based on the coupling power equation.
Referring to fig. 1, a flow chart of steps of the method for detecting crosstalk of a high-torsional-rate weak-coupling multi-core optical fiber according to the present invention specifically includes:
s1: based on the fiber twist rate, the core distance of the incident fiber and the interfered fiber, a twist correction coefficient characterizing the effect of the twist rate on the refractive index is constructed, expressed as:
Where D represents the core distance of the incident fiber from the interfered fiber and γ represents the fiber twist rate.
S2: according to the torsion correction coefficient, based on an equivalent propagation constant, obtaining a correction propagation constant:
angle of bend radial
Substituting the bending radial angle and the torsion correction coefficient k t into an expression of an equivalent propagation constant to obtain a correction propagation constant expression, wherein the correction propagation constant expression is expressed as:
Wherein, An initial phase established on a Cartesian coordinate system on a cross section of a weakly coupled multi-core optical fiber, wherein R represents the bending radius of the optical fiber; the equivalent propagation constant differences Deltabeta eq,mn＝βeq,m-βeq,n,βeq,m and beta eq,n respectively represent the equivalent propagation constants of the incident optical fiber m and the interfered optical fiber n, and the expression is thatThe undisturbed core propagation constant β c＝neff2π/λ,neff is the effective refractive index of the fundamental mode, λ is the wavelength of light, and (r, θ) is the angle of the local polar coordinates on the cross section of the weakly coupled multicore fiber in the bending radial direction.
S3: based on the coupling mode theory, introducing a correction propagation constant difference representing the bending radius of the optical fiber and the torsion rate of the optical fiber and a phase function representing the influence of random structural fluctuation, and constructing an updated coupling mode equation between the incident optical fiber and the interfered optical fiber of the weakly coupled multi-core optical fiber, wherein the updated coupling mode equation is expressed as follows:
Wherein, A m (z) and A n (z) respectively represent the electric field slow-changing amplitude of the incident optical fiber and the interfered optical fiber; z represents a longitudinal propagation distance, z=i×d, n=l/d, L is a fiber length of the weakly coupled multi-core fiber, N represents a total number of segments into which the weakly coupled multi-core fiber is divided, and d represents a length of each fiber segment; j represents a complex number, and K mn (z) represents a mode coupling coefficient from the incident optical fiber m to the interfered optical fiber n; Δβ eq,nm' represents the corrected propagation constant difference between the incident fiber m and the disturbed fiber n core, and is used to characterize the effect of fiber bend radius and fiber twist rate, expressed as:
let the incident optical fiber m be the central core and the interfered optical fiber n be the surrounding cores, correct the propagation constant difference to rewrite as:
f mn (z) denotes a phase function for describing the influence of random structural fluctuations, which is a smooth random process along the propagation direction.
S4: dividing the weakly coupled multi-core optical fiber into N irrelevant uniform sections with equal length, and calculating electric field slow-change amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber based on the updated coupling mode equation;
dividing the weakly coupled multicore fiber into N uncorrelated uniform segments of equal length, and considering that fiber bending and twisting results in phase uncorrelation of certain fiber segments; ignoring the fiber transmission loss, the amplitude a m (z) of the incident fiber m is denoted as a m(z)＝Am (0) =1; the amplitude a n (z) of the disturbed fiber n is denoted as a n (0) =0, and a n (z) < 1;
In the optical fiber segment [ z 1,z2 ], the power increase of the interfered optical fiber n is equivalent to the power increase of the inter-core crosstalk in the optical fiber segment [ z 1,z2 ], and is obtained according to the updated coupling mode equation, under the condition of low crosstalk, the electric field slowly-changing amplitude in the optical fiber segment [ z 1,z2 ] is changed into:
wherein β eq,m 'and β eq,n' represent corrected propagation constants of the incident optical fiber m and the interfered optical fiber n, respectively.
S5: acquiring an inter-core crosstalk power expression of the optical fiber section according to the electric field slow-change amplitude change in the same optical fiber section of the incident optical fiber and the interfered optical fiber;
Wherein, the expression is used for taking the average, Is an autocorrelation function of f nm (z), Δz=z 2-z1; z' represents an integral variable consistent with the z integral range; Δβ eq,nm' represents the corrected propagation constant difference between the incident optical fiber m and the interfered optical fiber n core.
S6: based on the correction propagation constant difference between the incident optical fiber and the interfered optical fiber and the inter-core crosstalk power expression, obtaining the inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber;
Putting together the crosstalk of several incoherent fiber sections, calculating the fiber crosstalk XT between the cores of the incident fiber m and the interfered fiber n:
Wherein i=1, 2,3,., N, β eq,n,i 'and β eq,m,i' are the equivalent propagation constants of the i-th section of interfered optical fiber N and the incident optical fiber m, respectively; z represents a longitudinal propagation distance, z=i×d, n=l/d, L is a fiber length of the weak-coupling multi-core fiber, and N represents a total number of segments of the weak-coupling multi-core fiber that are segmented; k nm,i (z) represents the mode coupling coefficient of the interfered optical fiber n and the incident optical fiber m in the i-th segment.
S7: substituting a power spectrum density function corresponding to a random process of random structural fluctuation into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model;
random structural fluctuations are uncertain, and are assumed to be a smooth random process along the propagation direction, and the power spectral density function of the random structural fluctuations is obtained through Fourier transformation by using an ensemble averaging method;
S71: research has analyzed that when f mn (z) includes only the random structural effects of structural fluctuations, but not the effects of bending and warping, different types of autocorrelation functions of f mn (z) were studied, and exponential autocorrelation functions were found to be most suitable, thus using fourier transforms to obtain the power spectral density function of the random process of random structural fluctuations, expressed as:
s72: substituting the calculated model into the inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber to obtain an inter-core crosstalk calculation model, wherein the calculated model is expressed as follows:
the preset correlation length l c represents a parameter of a power spectrum density function of a random process representing random structural fluctuation after Fourier transformation, and the numerical value of the parameter represents the influence of the random structural fluctuation.
S8: and substituting the total number N of the segmented segments of the weakly coupled multi-core optical fiber, the mode coupling coefficient, the longitudinal propagation distance, the length of each optical fiber segment, the preset correlation length and the correction propagation constant difference into an inter-core crosstalk calculation model to obtain a high-torsion-rate weakly coupled multi-core optical fiber crosstalk value.
Referring to FIG. 2, a dual core fiber mode coupling schematic diagram of a multi-core fiber system with a core number of 2 according to one embodiment of the present invention is shown; in this case, in weakly coupled multicore fibers, the main internal factors of inter-core crosstalk (ICXT) are core spacing, refractive index differences, and random structural fluctuations, without regard to fiber loss.
According to the high-speed weak-coupling multi-core optical fiber crosstalk detection method, the influence of the bending radius of the optical fiber, the torsion speed of the optical fiber and random structural fluctuation is introduced to construct and update the coupling mode equation, so that the error estimation of the influence of the traditional model on the torsion speed is made up, the influence of the random structural fluctuation caused by bending, torsion and environment in the actual laying process of the optical fiber is considered, and the calculation accuracy of crosstalk values is improved. The application range is wider, and the method is suitable for not only the phase matching area but also the non-phase matching area; and is equally applicable to homogeneous and heterogeneous multicore fibers.
Based on the embodiment, the crosstalk calculation model in the high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method provided by the invention is utilized to compare with the existing model, and the accuracy of the crosstalk calculation model provided by the invention is verified; the present example uses a seven-core optical fiber as shown in fig. 3, and the parameters of the seven-core optical fiber are shown in table 1:
table 1: seven-core optical fiber parameters
Based on the seven-core optical fiber parameter setting simulation parameters, the high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method (RAM) provided by the invention is compared with the calculated estimated values of the existing Koshiba expression and Adolfo expression and the numerical simulation result (Sim): referring to fig. 4, a graph of the comparison of crosstalk with the bend radius of the optical fiber at a twist rate γ=1pi/m is shown; referring to fig. 5, a graph of the comparison of crosstalk with the bend radius of the optical fiber at a twist rate γ=50pi/m is shown.
As can be seen from fig. 4 and 5, at low torsion rates, SAM is well matched with the numerical simulation results, while the estimate of Koshiba expression is almost identical with SAM; however, the Adolfo expression gives a very small estimate because the Adolfo expression is very sensitive to torsion rate and is not suitable for low-rotation curvatures; the expression predictors for SAM and Adolfo are less than Koshiba expression at high skew rates. The twist rate reduces crosstalk and this reduction is achieved at high twist rates. This is due to the difference in propagation constants between the interfering and interfered cores, which increases due to the high twist curvature. These simulation results also agree well with the previous simulation and experimental results.
In order to further study the effect of the twist rate on the inter-core crosstalk power, the effect of the twist rate in the phase matching region and the non-phase matching region was analyzed, and it can be seen that the numerical simulation result is better matched with the estimated value of the SAM. Referring to FIG. 6, a comparison of simulation results of crosstalk as a function of fiber twist rate in a phase matching region is shown; referring to fig. 7, a comparison of simulation results of crosstalk as a function of fiber twist rate is shown in a non-phase matching region.
Referring to fig. 6 and 7, it can be seen that the SAM and Koshiba expressions have the same simulation result under a certain range of torsion rate, but above the torsion rate, the SAM simulation result shows a tendency of increasing and then decreasing with increasing torsion rate, and the suppression effect of inter-core crosstalk is very remarkable under a very high torsion rate. Also, the simulation results expressed at Adolfo were relatively small at low twist rates and Adolfo were oscillatory at high twist rates, i.e., adolfo showed reduced effects on inter-core crosstalk power only over certain twist rate intervals.
At high twist curvatures, SAMs exhibit different phenomena in phase matching and non-PMR, since high twist rates change the inherent effective index of the core, thereby increasing the propagation constant difference between cores. Referring to fig. 8, a schematic diagram showing the comparison of the crosstalk variation between SAM and numerical simulation results provided by the present invention at different torsion rates is shown; as can be seen from fig. 8, the critical bending radius becomes smaller with an increase in the twist rate, which is consistent with the conventional phenomenon that the critical bending radius becomes smaller, and its root is an increase in the difference in the intrinsic effective refractive index, which is consistent with the prediction of the corrected propagation constant, wherein the twist correction coefficient k t contributes to both the intrinsic effective refractive index and the refractive index change due to bending.
In case both a long preset correlation length and a high torsion rate reduce crosstalk, it is necessary to explore the applicability of both. Referring to fig. 9, a graph is shown that is a comparison of crosstalk with the bending radius of the optical fiber at different preset correlation lengths l c at a torsion rate γ=0.01 pi/m; referring to fig. 10, a graph is shown that is a comparison of crosstalk with the bending radius of the optical fiber at different preset correlation lengths l c at a torsion rate γ=100deg.pi/m.
As can be seen from fig. 9 and 10, the crosstalk reduction effect of the high twist rate is applicable to both the phase matching region and the non-phase matching region, but is more remarkable in the phase matching region, whereas the crosstalk reduction effect of the long correlation length is applicable to only the non-phase matching region. This is because in the phase matching region, the disturbance due to bending is much larger than that due to structural fluctuations. However, high slew rate disturbances have a strong impact on both the phase-matched and non-phase-matched regions.
Referring to fig. 11, a graph showing propagation constant difference under the influence of torsion is shown; the upper graph is a corrected propagation constant difference change graph constructed based on the corrected propagation constant, and the lower graph is an equivalent propagation constant difference change graph constructed based on the equivalent propagation constant. The high twist rate affects the phase and changes the magnitude of the propagation constant difference because the high twist changes the refractive index of the core. In the conventional model, since the propagation constant difference is calculated by using the amplitudes of the cores after the N phase matching points, but the twisting affects only the phase and does not affect the amplitude, the crosstalk reduction due to the increase of the propagation constant difference cannot be observed, and the above-described method of using the segmentation in the derivation is based on such consideration.
In summary, the SAM of the high torsional rate weak coupling multi-core optical fiber crosstalk detection method provided by the present invention is a very effective method for estimating the power of the inter-core crosstalk ICXT, but the segment length of the SAM may affect the operation time and the SAM accuracy. To this end, it is desirable to explore suitable segment lengths, making SAM operations relatively faster, while maintaining accuracy. Theoretically, the shorter the segment length, the more accurate the result, but the longer the corresponding calculation time. First, crosstalk value XT is calculated at segment length d=0.1 mm and is used as a reference value for comparison, and then XT calculated for other different segment length d values is compared with the reference value, thereby selecting an appropriate value interval for segment length d. Referring to FIG. 12, a graph showing the relative error as a function of segment length is shown, showing the relative error |DeltaXT| for segment length d taken from 0.1mm to 100 mm. The relative error |Δxt| is given by:
As can be seen from fig. 12, when the length of the line segment is smaller than 10mm, the relative error is smaller than 0.001%, and when the length of the line segment is larger, the error tends to increase exponentially. Therefore, the SAM provided by the present invention provides a very accurate estimation result when the segment length value is below 10 mm. The invention has the segment length of 1mm when being simulated, and the SAM obviously provides a very accurate inter-core crosstalk power estimation method under the segment length.
Based on the above embodiment, the embodiment of the present invention further provides a high-torsional-rate weak-coupling multi-core optical fiber crosstalk detection device, including:
The correction propagation constant acquisition module 100 is configured to construct a torsion correction coefficient that characterizes an influence of the torsion rate on the refractive index based on the fiber torsion rate and a core distance between the incident fiber and the interfered fiber; acquiring a correction propagation constant based on the propagation constant according to the torsion correction coefficient;
The updated coupling mode equation construction module 200 is configured to introduce a correction propagation constant difference representing a bending radius of the optical fiber and a torsion rate of the optical fiber, and a phase function representing an influence of random structural fluctuation based on a coupling mode theory, and construct an updated coupling mode equation between an incident optical fiber and an interfered optical fiber of the weakly coupled multi-core optical fiber;
The inter-core crosstalk power calculation module 300 is configured to divide the weakly coupled multi-core optical fiber into N equal-length uncorrelated uniform segments, and calculate electric field slow-variation amplitude changes in the same optical fiber segment of the incident optical fiber and the interfered optical fiber based on the updated coupling mode equation; acquiring an inter-core crosstalk power expression of the optical fiber section according to the electric field slow-change amplitude change in the same optical fiber section of the incident optical fiber and the interfered optical fiber;
the inter-core crosstalk calculation model obtaining module 400 is configured to obtain an inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber based on the corrected propagation constant difference between the incident optical fiber and the interfered optical fiber and the inter-core crosstalk power expression; substituting a power spectrum density function corresponding to a random process of random structural fluctuation into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model;
The inter-core crosstalk value calculation module 500 is configured to obtain a high-torsion-rate weak-coupling multi-core optical fiber crosstalk value according to the total number N of segmented segments of the weak-coupling multi-core optical fiber, the mode coupling coefficient, the longitudinal propagation distance, the length of each optical fiber segment, the correlation length, and the correction propagation constant difference, which are substituted into the inter-core crosstalk calculation model.
The high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection device of the present embodiment is used to implement the foregoing high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method, so the specific embodiment of the high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection device can be seen from the foregoing embodiment part of the high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method, for example, the correction propagation constant obtaining module 100 is used to implement steps S1 and S2 in the foregoing high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method; updating the coupling mode equation construction module 200 to implement step S3 in the high-torsional-rate weak-coupling multi-core optical fiber crosstalk detection method; the inter-core crosstalk power calculation module 300 is configured to implement steps S4 and S5 in the high-torsional-rate weak-coupling multi-core optical fiber crosstalk detection method; the inter-core crosstalk calculation model module 400 is configured to implement steps S6 and S7 in the high-torsional-rate weak-coupling multi-core optical fiber crosstalk detection method; the inter-core crosstalk value calculating module 500 is configured to implement step S8 in the high-torsional-rate weak-coupling multi-core optical fiber crosstalk detection method, so the specific implementation manner thereof may refer to the description of the corresponding embodiments of each portion, which is not repeated herein.
Based on the above embodiments, the present invention further provides a computer readable storage medium, where a computer program is stored, where the computer program is executed by a processor to implement the steps of the high-torsion-rate weak-coupling multi-core optical fiber crosstalk detection method.
According to the high-speed weak-coupling multi-core optical fiber crosstalk detection method, the influence of the bending radius of the optical fiber, the torsion speed of the optical fiber and random structural fluctuation is introduced to construct and update the coupling mode equation, so that the error estimation of the influence of the traditional model on the torsion speed is made up, the influence of the random structural fluctuation caused by bending, torsion and environment in the actual laying process of the optical fiber is considered, and the calculation accuracy of crosstalk values is improved. Based on the coupling mode equation of the influence to be considered in the linear region, a coupling power equation is constructed to calculate multi-core optical fiber crosstalk, the multi-core optical fiber crosstalk calculation is more suitable for the practical optical fiber laying condition, the application range is wider, and the multi-core optical fiber crosstalk calculation method is suitable for not only the phase matching region but also the non-phase matching region, and is also suitable for homogeneous and heterogeneous multi-core optical fibers. Compared with a model without torsional and random structure fluctuation influence, the crosstalk calculation model provided by the invention can provide a quick and accurate crosstalk estimation for a modern communication system, is more suitable for the actual optical fiber laying condition, and has a wider application range. Based on the theoretical model, the crosstalk characteristics in different communication systems are more conveniently researched; according to the characteristics of crosstalk in different working intervals and the relation between the crosstalk and optical fiber parameters, a theoretical method for reducing the inter-core crosstalk is further researched.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (7)
1. The method for detecting the crosstalk of the high-torsion-rate weak-coupling multi-core optical fiber is characterized by comprising the following steps of:
based on the fiber twist rate, the core distance of the incident fiber and the interfered fiber, a twist correction coefficient characterizing the effect of the twist rate on the refractive index is constructed, expressed as: Wherein D represents the core distance between an incident optical fiber and an interfered optical fiber, and gamma represents the optical fiber torsion rate;
According to the torsion correction coefficient, based on an equivalent propagation constant, obtaining a correction propagation constant includes: will bend radial angle Substituting the correction coefficient k t into an expression of an equivalent propagation constant to obtain a correction propagation constant expression, wherein the correction propagation constant expression is expressed as: Wherein, An initial phase established on a Cartesian coordinate system on a cross section of a weakly coupled multi-core optical fiber, wherein R represents the bending radius of the optical fiber; the equivalent propagation constant differences Deltabeta eq,mn＝βeq,m-βeq,n,βeq,m and beta eq,n respectively represent the equivalent propagation constants of the incident optical fiber m and the interfered optical fiber n, and the expression is thatThe undisturbed fiber core propagation constant beta c＝neff2π/λ,neff is the effective refractive index of the fundamental mode, lambda is the wavelength of light, and (r, theta) is the angle of the local polar coordinate on the cross section of the weakly coupled multi-core fiber in the bending radial direction;
based on the coupling mode theory, introducing a correction propagation constant difference representing the bending radius of the optical fiber and the torsion rate of the optical fiber and a phase function representing the influence of random structural fluctuation, and constructing an updated coupling mode equation between the incident optical fiber and the interfered optical fiber of the weakly coupled multi-core optical fiber, wherein the updated coupling mode equation is expressed as follows: Wherein, A m (z) and A n (z) respectively represent the electric field slow-changing amplitude of the incident optical fiber and the interfered optical fiber; z represents a longitudinal propagation distance, z=i×d, n=l/d, L is a fiber length of the weakly coupled multi-core fiber, N represents a total number of segments into which the weakly coupled multi-core fiber is divided, and d represents a length of each fiber segment; j represents a complex number, and K mn (z) represents a mode coupling coefficient from the incident optical fiber m to the interfered optical fiber n; Δβ eq,nm' represents the corrected propagation constant difference between the incident fiber m and the disturbed fiber n core, and is used to characterize the effect of fiber bend radius and fiber twist rate, expressed as: let the incident optical fiber m be the central core and the interfered optical fiber n be the surrounding cores, correct the propagation constant difference to rewrite as: f mn (z) denotes a phase function for describing the influence of random structural fluctuations, a smooth random process along the propagation direction;
dividing the weakly coupled multi-core optical fiber into N irrelevant uniform sections with equal length, and calculating electric field slow-change amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber based on the updated coupling mode equation;
Acquiring an inter-core crosstalk power expression of the optical fiber section according to the electric field slow-change amplitude change in the same optical fiber section of the incident optical fiber and the interfered optical fiber;
Based on the correction propagation constant difference between the incident optical fiber and the interfered optical fiber and the inter-core crosstalk power expression, obtaining the inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber;
Substituting a power spectrum density function corresponding to a random process of random structural fluctuation into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model;
Substituting the total number N of segmented segments of the weakly coupled multi-core optical fiber, the mode coupling coefficient, the longitudinal propagation distance, the length of each optical fiber segment, the preset correlation length and the correction propagation constant difference into an inter-core crosstalk calculation model to obtain a high-torsion-rate weakly coupled multi-core optical fiber crosstalk value.
2. The method for detecting crosstalk between high-torsional-rate weakly-coupled multi-core fibers according to claim 1, wherein the step of dividing the weakly-coupled multi-core fibers into N equal-length uncorrelated uniform segments and calculating the electric field slow-variation amplitude variations in the same fiber segment of the incident fiber and the interfered fiber based on the updated coupling equation comprises:
Dividing the weakly coupled multi-core optical fiber into N uncorrelated uniform segments with equal length, ignoring the optical fiber transmission loss, and representing the amplitude A m (z) of the incident optical fiber m as A m(z)＝Am (0) =1; the amplitude a n (z) of the disturbed fiber n is denoted as a n (0) =0, and a n (z) =1;
In the optical fiber segment [ z 1,z2 ], the power increase of the interfered optical fiber n is equivalent to the power increase of the inter-core crosstalk in the optical fiber segment [ z 1,z2 ], and is obtained according to the updated coupling mode equation, under the condition of low crosstalk, the electric field slowly-changing amplitude in the optical fiber segment [ z 1,z2 ] is changed into:
wherein β eq,m 'and β eq,n' represent corrected propagation constants of the incident optical fiber m and the interfered optical fiber n, respectively.
3. The method for detecting the crosstalk between the cores of the high-torsional-rate weakly coupled multi-core optical fiber according to claim 2, wherein the obtaining the inter-core crosstalk power expression of the optical fiber section according to the electric field slowly varying amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber is expressed as:
Wherein, the expression is used for taking the average, Is an autocorrelation function of f nm (z), Δz=z 2-z1; z' represents an integral variable consistent with the z integral range; Δβ eq,nm' represents the corrected propagation constant difference between the incident optical fiber m and the interfered optical fiber n core.
4. The method for detecting crosstalk between high-torsional-rate weakly-coupled multi-core fibers according to claim 3, wherein the obtaining of the inter-core crosstalk expression between the incident fiber and the interfered fiber based on the corrected propagation constant difference between the incident fiber and the interfered fiber and the inter-core crosstalk power expression is expressed as:
Where i=1, 2,3, N, β eq,n,i 'and β eq,m,i' are the corrected propagation constants of the i-th section of the interfered optical fiber N and the incident optical fiber m, respectively; z represents a longitudinal propagation distance, z=i×d, n=l/d, L is a fiber length of the weak-coupling multi-core fiber, and N represents a total number of segments of the weak-coupling multi-core fiber that are segmented; k nm,i (z) represents the mode coupling coefficient of the interfered optical fiber n and the incident optical fiber m in the i-th segment.
5. The method for detecting crosstalk between high-torsional-rate weakly-coupled multi-core fibers according to claim 4, wherein substituting a power spectral density function corresponding to a random process of random structural fluctuations into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model comprises:
The power spectral density function of a random process that utilizes fourier transforms to obtain random structural fluctuations is expressed as:
Substituting the calculated model into the inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber to obtain an inter-core crosstalk calculation model, wherein the calculated model is expressed as follows:
The preset correlation length l c represents parameters of a power spectrum density function of a random process of random structural fluctuation after Fourier transformation, and the numerical value of the parameters represents the influence of the random structural fluctuation.
6. A high torsional rate weakly coupled multi-core fiber crosstalk detection device, comprising:
the correction propagation constant acquisition module is used for constructing a torsion correction coefficient representing the influence of the torsion rate on the refractive index based on the fiber torsion rate and the fiber core distance between the incident fiber and the interfered fiber, and the torsion correction coefficient is expressed as: Wherein D represents the core distance between an incident optical fiber and an interfered optical fiber, and gamma represents the optical fiber torsion rate; according to the torsion correction coefficient, based on an equivalent propagation constant, obtaining a correction propagation constant includes: will bend radial angle Substituting the correction coefficient k t into an expression of an equivalent propagation constant to obtain a correction propagation constant expression, wherein the correction propagation constant expression is expressed as: Wherein, An initial phase established on a Cartesian coordinate system on a cross section of a weakly coupled multi-core optical fiber, wherein R represents the bending radius of the optical fiber; the equivalent propagation constant differences Deltabeta eq,mn＝βeq,m-βeq,n,βeq,m and beta eq,n respectively represent the equivalent propagation constants of the incident optical fiber m and the interfered optical fiber n, and the expression is thatThe undisturbed fiber core propagation constant beta c＝neff2π/λ,neff is the effective refractive index of the fundamental mode, lambda is the wavelength of light, and (r, theta) is the angle of the local polar coordinate on the cross section of the weakly coupled multi-core fiber in the bending radial direction;
The updated coupling mode equation construction module is used for introducing a correction propagation constant difference representing the bending radius and the torsion rate of the optical fiber and representing a phase function of random structural fluctuation influence based on the coupling mode theory to construct an updated coupling mode equation between the incident optical fiber and the interfered optical fiber of the weakly coupled multi-core optical fiber, and is expressed as: Wherein, A m (z) and A n (z) respectively represent the electric field slow-changing amplitude of the incident optical fiber and the interfered optical fiber; z represents a longitudinal propagation distance, z=i×d, n=l/d, L is a fiber length of the weakly coupled multi-core fiber, N represents a total number of segments into which the weakly coupled multi-core fiber is divided, and d represents a length of each fiber segment; j represents a complex number, and K mn (z) represents a mode coupling coefficient from the incident optical fiber m to the interfered optical fiber n; Δβ eq,nm' represents the corrected propagation constant difference between the incident fiber m and the disturbed fiber n core, and is used to characterize the effect of fiber bend radius and fiber twist rate, expressed as: let the incident optical fiber m be the central core and the interfered optical fiber n be the surrounding cores, correct the propagation constant difference to rewrite as: f mn (z) denotes a phase function for describing the influence of random structural fluctuations, a smooth random process along the propagation direction;
The inter-core crosstalk power calculation module is used for dividing the weakly coupled multi-core optical fiber into N irrelevant uniform sections with equal length, and calculating the electric field slow-change amplitude variation in the same optical fiber section of the incident optical fiber and the interfered optical fiber based on the updated coupling mode equation; acquiring an inter-core crosstalk power expression of the optical fiber section according to the electric field slow-change amplitude change in the same optical fiber section of the incident optical fiber and the interfered optical fiber;
The inter-core crosstalk calculation model acquisition module is used for acquiring an inter-core crosstalk expression of the incident optical fiber and the interfered optical fiber based on the correction propagation constant difference between the incident optical fiber and the interfered optical fiber and the inter-core crosstalk power expression; substituting a power spectrum density function corresponding to a random process of random structural fluctuation into the inter-core crosstalk expression to obtain an inter-core crosstalk calculation model;
the inter-core crosstalk value calculation module is used for substituting the inter-core crosstalk calculation model according to the total number N of segmented segments of the weakly coupled multi-core optical fiber, the mode coupling coefficient, the longitudinal propagation distance, the length of each optical fiber segment, the correlation length and the correction propagation constant difference to obtain the high-torsion-rate weakly coupled multi-core optical fiber crosstalk value.
7. A computer readable storage medium, characterized in that the computer readable storage medium has stored thereon a computer program which, when executed by a processor, implements the steps of a high twist rate weakly coupled multicore fiber crosstalk detection method according to any of claims 1 to 5.
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